[Br-].[C:2]([CH2:7][S+](C)C)([O:4][CH2:5][CH3:6])=[O:3].N12CCCN=C1CCCCC2.[C:22]1(=[O:27])[CH2:26][CH2:25][CH:24]=[CH:23]1.Cl.[Cl-].[Na+]>C1(C)C=CC=CC=1>[O:27]=[C:22]1[CH2:26][CH2:25][CH:24]2[CH:23]1[CH:7]2[C:2]([O:4][CH2:5][CH3:6])=[O:3]A suspension of carboethoxymethyl dimethylsulfonium bromide (45.5 g) in toluene (350 mL) was treated with 1,8-diazabicyclo[5.4.0]undec-7-ene (30.2 g). The resulting mixture was stirred at room temperature. After one hour, the reaction mixture was treated with 2-cyclopenten-1-one (19.57 g). After an additional 18 hours, the reaction mixture was added to a 1N hydrochloric acid/sodium chloride solution. The resulting mixture was extracted with diethyl ether. The combined ether extracts were dried over magnesium sulfate, filtered, and concentrated in vacuo. The residue was purified using silica-gel chromatography, eluting with a linear gradient of 10% ethyl acetate/hexanes to 50% ethyl acetate/hexanes, to give 22.81 g of the title compound. Melting point: 36°-38° C.
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